HL7 OM1 General Segment
HL7 field reference OM1 fields from HL7 v2.5.1 Show fields
These are the generated fields for the version selected at the top of the page. The document stays the same, but the reference panel follows that version.
Fields
| Field | Name | Required | Repeatable | Type | Table |
|---|---|---|---|---|---|
| OM1.1 | Sequence Number - Test/Observation Master File | Yes | No | NM | |
| OM1.2 | Producer's Service/Test/Observation ID | Yes | No | CE | 9999 |
| OM1.3 | Permitted Data Types | No | Yes | ID | 0125 |
| OM1.4 | Specimen Required | Yes | No | ID | 0136 |
| OM1.5 | Producer ID | Yes | No | CE | 9999 |
| OM1.6 | Observation Description | No | No | TX | |
| OM1.7 | Other Service/Test/Observation IDs for the Observation | No | No | CE | 9999 |
| OM1.8 | Other Names | Yes | Yes | ST | |
| OM1.9 | Preferred Report Name for the Observation | No | No | ST | |
| OM1.10 | Preferred Short Name or Mnemonic for Observation | No | No | ST | |
| OM1.11 | Preferred Long Name for the Observation | No | No | ST | |
| OM1.12 | Orderability | No | No | ID | 0136 |
| OM1.13 | Identity of Instrument Used to Perform this Study | No | Yes | CE | 9999 |
| OM1.14 | Coded Representation of Method | No | Yes | CE | 9999 |
| OM1.15 | Portable Device Indicator | No | No | ID | 0136 |
| OM1.16 | Observation Producing Department/Section | No | Yes | CE | 9999 |
| OM1.17 | Telephone Number of Section | No | No | XTN | |
| OM1.18 | Nature of Service/Test/Observation | Yes | No | IS | 0174 |
| OM1.19 | Report Subheader | No | No | CE | 9999 |
| OM1.20 | Report Display Order | No | No | ST | |
| OM1.21 | Date/Time Stamp for any change in Definition for the Observation | No | No | TS | |
| OM1.22 | Effective Date/Time of Change | No | No | TS | |
| OM1.23 | Typical Turn-Around Time | No | No | NM | |
| OM1.24 | Processing Time | No | No | NM | |
| OM1.25 | Processing Priority | No | Yes | ID | 0168 |
| OM1.26 | Reporting Priority | No | No | ID | 0169 |
| OM1.27 | Outside Site(s) Where Observation may be Performed | No | Yes | CE | 9999 |
| OM1.28 | Address of Outside Site(s) | No | Yes | XAD | |
| OM1.29 | Phone Number of Outside Site | No | No | XTN | |
| OM1.30 | Confidentiality Code | No | No | CWE | 0177 |
| OM1.31 | Observations Required to Interpret the Observation | No | No | CE | 9999 |
| OM1.32 | Interpretation of Observations | No | No | TX | |
| OM1.33 | Contraindications to Observations | No | No | CE | 9999 |
| OM1.34 | Reflex Tests/Observations | No | Yes | CE | 9999 |
| OM1.35 | Rules that Trigger Reflex Testing | No | No | TX | |
| OM1.36 | Fixed Canned Message | No | No | CE | 9999 |
| OM1.37 | Patient Preparation | No | No | TX | |
| OM1.38 | Procedure Medication | No | No | CE | 9999 |
| OM1.39 | Factors that may Affect the Observation | No | No | TX | |
| OM1.40 | Service/Test/Observation Performance Schedule | No | Yes | ST | |
| OM1.41 | Description of Test Methods | No | No | TX | |
| OM1.42 | Kind of Quantity Observed | No | No | CE | 0254 |
| OM1.43 | Point Versus Interval | No | No | CE | 0255 |
| OM1.44 | Challenge Information | No | No | TX | 0256 |
| OM1.45 | Relationship Modifier | No | No | CE | 0258 |
| OM1.46 | Target Anatomic Site Of Test | No | No | CE | 9999 |
| OM1.47 | Modality Of Imaging Measurement | No | No | CE | 0259 |
OM1 is the general service/test/observation master record, the broad catalog entry many order and result workflows depend on.
The standard describes OM1 this way: The OM1 segment contains the attributes that apply to the definition of most observations. This segment also contains the field attributes that specify what additional segments might also be defined for this observation.
Master-file segments update reference data rather than describing a single patient event. They define locations, staff, providers, test catalogs, charge items, inventory items, languages, certificates, and other shared records.
Because many downstream messages depend on this data, small changes here can have large effects. Use stable identifiers, effective dates, action codes, and clear ownership rules instead of treating a master-file feed like a loose spreadsheet export.
The v2.5.1 structures show OM1 in MFN_M03 - Master file - test/observation, MFN_M08 - Test/observation (numeric) master file, MFN_M09 - Test/observation (categorical) master file, and MFN_M10 - Test /observation batteries master file, and 2 other message structures. That tells you where it can appear, but the implementation guide still decides which optional fields are meaningful.
For practical interface work, read the generated field panel for datatype, required, repeatable, and table details, then use the notes below to decide what the field should mean in the receiving workflow.
OM1-1 identifies the Sequence Number - Test/Observation Master File for this master-file record. Send the identifier that the receiving system actually keys on, and keep the assigning authority or coding system visible when the datatype supports it.
OM1-2 identifies the Producer's Service/Test/Observation ID for this master-file record. Send the identifier that the receiving system actually keys on, and keep the assigning authority or coding system visible when the datatype supports it.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-3 qualifies the master-file record rather than identifying it. This is the sort of field receivers often use for branching, filtering, or display grouping.
Use the agreed value set, starting from HL7 table 0125. A local code without an agreed coding system is a small ambiguity that becomes a mapping problem later.
OM1-4 describes specimen or container handling. This is not patient identity and not order identity; it is the physical or analyzer-side detail needed to move, test, store, or track the specimen correctly.
The generated panel links this to HL7 table 0136; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-5 identifies the Producer ID for this master-file record. Send the identifier that the receiving system actually keys on, and keep the assigning authority or coding system visible when the datatype supports it.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-6 is human-readable context. Keep it useful for display and troubleshooting, but do not hide required workflow logic here unless the implementation guide explicitly says the receiver parses it.
OM1-7 carries Other Service/Test/Observation IDs for the Observation for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-8 is a display, lookup, or reporting name for the master-file record. Keep the official code in the identifier field and use this field to help humans find or recognize the item.
Repeats are useful for aliases, local names, short names, or report labels, but do not make the receiver infer which one is primary without an agreed rule.
OM1-9 is a display, lookup, or reporting name for the master-file record. Keep the official code in the identifier field and use this field to help humans find or recognize the item.
OM1-10 is a display, lookup, or reporting name for the master-file record. Keep the official code in the identifier field and use this field to help humans find or recognize the item.
OM1-11 is a display, lookup, or reporting name for the master-file record. Keep the official code in the identifier field and use this field to help humans find or recognize the item.
OM1-12 carries Orderability for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0136; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-13 carries Identity of Instrument Used to Perform this Study for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-14 qualifies the master-file record rather than identifying it. This is the sort of field receivers often use for branching, filtering, or display grouping.
Use the agreed value set, starting from HL7 table 9999. A local code without an agreed coding system is a small ambiguity that becomes a mapping problem later.
OM1-15 tells the receiver the state of this master-file record. Status fields often drive workflow branches, so use the agreed code and do not infer a status just because another field looks complete.
The coded value should follow HL7 table 0136 or the narrower table in the local profile.
OM1-16 places the master-file record in an organization, facility, department, room, bed, or location group. Keep physical location, owning department, and receiving facility separate when the datatype allows it.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-17 is a count or total for this master-file record. Make the counting rule explicit before using it for reconciliation, billing, or workflow limits.
OM1-18 carries Nature of Service/Test/Observation for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0174; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-19 carries Report Subheader for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-20 carries Report Display Order for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
OM1-21 is a timing field. Send the real source-system precision, do not pad unknown dates or times, and agree how timezone offsets are handled when time of day matters.
OM1-22 is a timing field. Send the real source-system precision, do not pad unknown dates or times, and agree how timezone offsets are handled when time of day matters.
For effective and end dates, make the boundary rule explicit. Receivers need to know whether the value is inclusive, exclusive, planned, actual, or merely informational.
OM1-23 is a timing field. Send the real source-system precision, do not pad unknown dates or times, and agree how timezone offsets are handled when time of day matters.
OM1-24 is a timing field. Send the real source-system precision, do not pad unknown dates or times, and agree how timezone offsets are handled when time of day matters.
OM1-25 qualifies the master-file record rather than identifying it. This is the sort of field receivers often use for branching, filtering, or display grouping.
Use the agreed value set, starting from HL7 table 0168. A local code without an agreed coding system is a small ambiguity that becomes a mapping problem later.
OM1-26 qualifies the master-file record rather than identifying it. This is the sort of field receivers often use for branching, filtering, or display grouping.
Use the agreed value set, starting from HL7 table 0169. A local code without an agreed coding system is a small ambiguity that becomes a mapping problem later.
OM1-27 qualifies the master-file record rather than identifying it. This is the sort of field receivers often use for branching, filtering, or display grouping.
Use the agreed value set, starting from HL7 table 9999. A local code without an agreed coding system is a small ambiguity that becomes a mapping problem later.
OM1-28 carries contact details. Use the datatype components for use code, equipment type, address type, country, and other qualifiers rather than squeezing everything into one formatted string.
This field can repeat. Use repetitions for separate real-world values, not as a workaround for putting several unrelated ideas in one field.
OM1-29 is a count or total for this master-file record. Make the counting rule explicit before using it for reconciliation, billing, or workflow limits.
OM1-30 identifies the Confidentiality Code for this master-file record. Send the identifier that the receiving system actually keys on, and keep the assigning authority or coding system visible when the datatype supports it.
The generated panel links this to HL7 table 0177; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-31 carries Observations Required to Interpret the Observation for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-32 carries Interpretation of Observations for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
OM1-33 carries Contraindications to Observations for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-34 carries Reflex Tests/Observations for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-35 carries Rules that Trigger Reflex Testing for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
OM1-36 carries Fixed Canned Message for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-37 carries Patient Preparation for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
OM1-38 belongs to the medication/treatment workflow. Be explicit about whether the value describes the original order, encoded order, dispense event, scheduled give, or actual administration.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-39 carries Factors that may Affect the Observation for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
OM1-40 carries Service/Test/Observation Performance Schedule for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
This field can repeat. Use repetitions for separate real-world values, not as a workaround for putting several unrelated ideas in one field.
OM1-41 is human-readable context. Keep it useful for display and troubleshooting, but do not hide required workflow logic here unless the implementation guide explicitly says the receiver parses it.
OM1-42 carries a measured, counted, priced, or dosed value. A number without the expected unit, currency, or companion qualifier is much easier to misread than an empty field.
The generated panel links this to HL7 table 0254; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-43 carries Point Versus Interval for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0255; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-44 carries Challenge Information for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0256; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-45 carries Relationship Modifier for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0258; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM1-46 qualifies the master-file record rather than identifying it. This is the sort of field receivers often use for branching, filtering, or display grouping.
Use the agreed value set, starting from HL7 table 9999. A local code without an agreed coding system is a small ambiguity that becomes a mapping problem later.
OM1-47 carries Modality Of Imaging Measurement for this master-file record. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0259; many real interfaces narrow that list further, so follow the receiver's implementation guide.
Related links
- MFI - Master File Identification
- MFE - Master File Entry
- MFA - Master File Acknowledgment
- LOC - Location Identification
- STF - Staff Identification
- PRA - Practitioner Detail
- CDM - Charge Description Master
- MFN_M03 - Master file - test/observation
- MFN_M08 - Test/observation (numeric) master file
- MFN_M09 - Test/observation (categorical) master file